Cruise ships promote themselves a fun-filled way to take a vacation but there is a dark side to these "floating cities". Some cruise ships hold up to 5,000 people and most of their waste is dumped directly into the ocean. This waste includes untreated sewage and inadvertent trash. Powering a ship that large with dirty crude oil causes an incredible amount of carbon pollution and smog. Environmental laws have not kept pace with growth of the industry.